Natural gas storage

PG&E customers rely on the safe and reliable delivery of natural gas to their homes and businesses every day. In order to provide natural gas to our customers, PG&E owns and maintains more than 6,000 miles transmission pipelines, 42,000 miles distribution pipelines and three natural gas storage facilities. During the five-month winter heating season, when demand is highest, gas is withdrawn from underground storage facilities to meet the needs of customers. Gas storage also allows to us to maintain lower and more consistent gas prices throughout the year because we are able to utilize our supplies while prices for gas are typically more volatile and higher in other parts of the country.

Additionally, Natural gas provides 44 percent of all electric generation in California, more electricity generation than any energy source in California. (According to the California Energy Commission, data gathered as of September 10, 2015 - Read more about Total Electricity System Power*.)

About PG&E's Gas Storage Facilities

PG&E owns and operates 116 wells at 3 natural gas storage fields located in California and is a partner in fourth storage field. McDonald Island serves as the largest of PG&E's three facilities and is located in a scarcely populated area near the Sacramento-San Juaquin River Delta. The additional two facilities owned and operated by PG&E, Pleasant Creek and Los Medanos, are considerably small by industry standards.

PG&E uses multiple layers of protection to ensure the safe operation of our gas storage facilities. The company conducts daily leak inspections, weekly well pressure monitoring, as well as routine noise and temperature checks and subsurface safety valve tests to regularly assess the overall integrity of our facilities.

PG&E has a comprehensive asset and risk management program in place based on the practices supported by the International Organization for Standardization (ISO). To validate the effective implementation of these best practices, PG&E regularly seeks out third-party verification and became one of the first utilities to earn two of the highest internationally recognized asset management certifications—ISO 55001 and Publicly Available Specification (PAS) 55-1.

PG&E worked closely with the State of California Department of Conservation, Division of Oil, Gas and Geothermal Resources (DOGGR), the California Public Utilities Commission (CPUC) and other stakeholders to ensure that we were in full compliance with the state’s directives.

Pleasant Creek

Pleasant Creek is PG&E’s smallest storage facility and has a maximum capacity of 2.0 BCF. The facility is located in Yolo County and contains seven wells.

Los Medanos

Los Medanos is PG&E’s second largest facility and has a maximum capacity of 17.9 BCF. The facility is located in Contra Costa County. There are a total of 22 wells.

McDonald Island

McDonald Island is PG&E’s largest gas storage field and has a maximum capacity of 82 BCF. The facility is located on a man-made island in a scarcely populated agricultural area in the Sacramento-San Joaquin River Delta. There are 87 total wells, 81 of which operate for injection and withdrawal and six operate as observation wells. McDonald Island is capable of providing 25 percent of Northern California’s winter peak-day gas demand.

Update about McDonald Island

In June 2016, PG&E found leak indications during daily leak inspections. The amount of gas detected is so small that it falls below flow-rate measurable thresholds for instruments. There is currently no safety, health, environmental or reliability risk. As part of our comprehensive integrity management program and risk assessment procedures, PG&E immediately engaged necessary state agencies as well as other third party gas storage well experts.

PG&E experts and engineers are working with DOGGR and industry experts to determine what's causing the minor leaks. Noise-temperature surveys are being conducted at all 87 wells to identify the potential source(s) of the minor gas leaks.

While efforts are underway to identify the leak and develop repair plans, daily leak surveys and inspections continue, as well as monitoring and logging observations of the wells at the center of this incident.

We're using our vehicle-mounted leak detection technology that is 1,000 times more sensitive than traditional technologies to evaluate any change in the gas leaks. Additionally, we are using infrared cameras as part of these survey activities.

Aerial leak surveys were conducted on June 21 and 23 and the results are comparable methane emission rates from measurements obtained prior to the identified situation.

Montrose Air Quality Services, the nation's largest emissions testing service, tested the minor leaks on Tuesday, June 21. The leaks are so small that there is not enough gas being released to measure their flow-rate.

While there are no immediate risks to safety, health, or the environment, out of an abundance of caution, the injection and withdrawal of natural gas at McDonald Island is temporarily on hold. This also helps facilitate monitoring and inspection activities.

Please check back for regular updates.